Method of preparing animal glue



2,741,576 I METHOD on PREPARING ANIMAL GLUE Havard L. Keil, Clarendon lliills, IIL, assignor to Armour and Company, Chicago, Ill, a corporation of Illinois No Drawing. Application December 15, 1954,

Serial No. 475,576

l lClaims. or. ress This invention relates to a process for preparing animal glue. More particularly, this invention relates to an improved method for conditioning glue stock in preparing the same for glue extraction and to a method for recovering the glue therefrom. The method has particular usefulness in connection with the processing of hide stock materials. p

The conventional procedures for lime-conditioning glue stock of various types and processing the conditioned stock to recover the glue content and by-products therefrom is described in detail in a publication by Hull and Bangert, Ind. and Eng. Chem, 44-, 2275 1952). With reference to the raw materials which require a liming procedure for conditioning the stock before. the glue can be satisfactorily extracted, the procedure sets forth the following sequence steps: (a) the fresh or" salted raw materials are washed, preferably in a cone-type wash mill to remove salt and/or dirt and extraneous matter, (b) the stock is drained and covered with a lime solution and rolled or agitatedin the mill for several hours, ('0) the limed material is transferred to cement liming vats where it is covered with lime solution and stored for about 60 days to allow the stock to become properly conditioned for glue extraction, '(d) at the end of the 60 day period, the conditioned stock is Washed in a Wash mill for about 10 hours and sulfurous acid is added to neutralize the stock, (e) after a final wash the material is cooked in water in successive stages at progressively increasing temperatures from 155 to 212 F. to recover the glue and grease.

In connection with the prolonged storage of the raw materials in lime for a minimum of 60 days, several precautions must be exercised to avoid yield losses and quality impairment of the glue and by products. For example, it is usually necessary to drain the lime solution and add fresh batches to obtain satisfactory COIldlr tioning without excessive spoilage and deterioration. It may also be necessary to move the raw material from one vat to another to ensure complete exposure of the stock.

Despite these inherent diihculties which include prolonged periods of time for proper conditioning of the glue stock, considerable physical handling of the material and the use of a large quantity of chemical reagents such as lime needed in the multipleliming steps, the conventional procedure described in the publication has been in Widespread usage over a period of many years. Although alternative procedures directed to changing the process have been suggested from time to time, no significant change has been adopted to any extent by'tiie industry. The main reason for this resistance to. change has been the fact that the suggested alternative procedures for improving the process usually necessitate the installation of new equipment and facilities. The expense. involved is of such'a magnitude thatthe advantages. de' rived from the use of the proposed alternative procedures generally does not justify the drastic changes which are involved. Accordingly, a definite need exists for imice provements inthe lime-conditioning process which diminish or cli'minatesome or all of the aforementioned disadvantages which, at the same time, require little or no changes with respect to the installations and equipment currently used by glue manufacturers.

It is accordingly an object of this invention to provide an improved process tor conditioning glue stock with lime in a much shorter period of time than heretofore required. It is another object of this invention to provide an improved process for conditioning glue stock wherein the conventional equipment used by glue manufacturers can be fully utilized. It is a still further object to provide a new process for manufacturing animal glue of high quality which requires a reduced amount of physical handling and a smaller quantity of chemical reagents as compared to the requirements of the conventional limeconditionihg process. It is yet another object to provide a'novel process for preparing glue from cattle hide glue stock which achieves the objects just stated, and at the same time produces high yields of excellent quality'glue from thestandpoint of gel strength and viscosity. It is a still further object to provide a novel processffor conditioning glue stock which minimizes the loss of valuable by-products such as fats, grease, etc. Further objects and advantages will appear as the specification proceeds.

In one of its aspects, this invention is concerned with a method of treating collagen-bearing animal tissues with lime to condition the material for glue extraction, which method is characterized by the inclusion of a preliminary step of subjecting the glue stock to the action of added living and growing yeast or yeast-like organisms to par;- tially condition the stock. By virtue of the partial conditioning or pretreatment effected by the action ofspecific.

microorganisms on the glue stock, the material has been found to be exceedingly more responsive to the action of lime thereon whereby it now becomes possible to completely condition the stock for glue extraction in only a few days. Another aspect of this invention is concerned with a method for conditioning glue stock with lime for glue extraction, characterized by the aforementioned partial conditioning step and by the further step of simultaneously incorporating a selective bactericidal agent in the. microorganism containing medium whereby the action of the yeast or yeast-like organisms is unimpaired but putrefactive and destructive organisms are effectively destroyed. The combined operation has been found to be very effective against yield. losses and impairment of the quality of the recovered glue and by-products from the glue stock. A further aspect of this invention is concerned with methods of extracting the glue from glue stock conditioned in accordance with the procedure hereinafter discussed in detail wherein the pH control, and careful neutralization techniques are no longer required and at the same time the ash content of the extracted glue is kept at a minimum value.

As a starting material for use in the process of this invention, any collagen-bearing animal tissue can be used that normally requires the conventional lime-conditioning before its collagen content can be satisfactorily extracted with hot water to yield glue. This includes such raw materials as hide stock, trimmings, noses, pates, ears, tails, etc., invfresh or salted condition as conventionally made available to glue manufacturers. Salted stock constitutes. the more important source of raw material for glue manufacture. The present process realizes its. greatest advantage in the preparation of hide'glue and, there i salt if the material has been previously salted as well as dirt and other foreign matter accumulated thereon in the 3 process of handling prior to its becoming aavilable to the glue maker as glue stock.

Otherwise, the microorganisms are added directly to the bath, preferably in the form of an aqueous broth in order Among the various microorganisms which can be employed for partially conditioning the stock are the true yeasts of the tribe Saccharomyceteac. The genus Saccharomyces ciassified thereunder includes most of the commercial yeasts such as bakers yeast, brewers yeast, etc., which are identified as S. cerevisiae and S. carlsbergensis. In addition to these true yeasts, various yeastlike organisms such as li fycoderma ($12.) and Torulopsix (Sp.) can also be used. The use of these microorganisms in conjunction with an acidified aqueous plumping of the stock for conditioning the material is described in copending patent applications, Serial No. 243,378, filed August 23, 1951, and Serial No. 339,166, filed February 26, 1953.

Of the aforementioned yeasts and yeast-like organisms collectively referred to hereinafter as yeast-type organisms which exhibit a favorable hide conditioning action without proteolysis, it is preferred to use the true yeasts of the 1 genus Saccharomyces and the species cerevisiae (bakers yeast) is particularly desirable in view of its availability and relatively low cost.

, The mechanism of the partial conditioning reaction is not clearly understood but it has been determined on the basis of conventional tyrosine tests that little or no proteolytic activity is involved. The partial conditioning is thus seen to be dependent upon the function of living or vegetative microorganisms.

In order to eliminate putrefactive bacteria and molds from the glue stock, several methods of treatment can be used. For example, the washed and drained stock can be sterilized before the addition of the microorganisms with a germicidal agent such as hydrogen peroxide. One advantageof using hydrogen peroxide for this purpose is that it can be readily destroyed with catalase after the stock has been sterilized. Further, the initial use of hydrogen peroxide appears to enhance the effectiveness of the succeeding steps used for conditioning the stock for glue extraction. About 1% of a 30% hydrogen peroxide solution added to the water covered stock and allowed to remain in contactthcrewith for about 2 to 3 hours at room temperature or thereabouts is generally sufiicient for accomplishing the desired result.

While the above method for eliminating putrefactive organisms is entirely satisfactory as a preliminary step, it is usually desirable to take further precautions to avoid putrefaction during the microorganism treatment step, particularly when slightly elevated temperatures are used. For this purpose, a selective bactericide such as a silicofluoride salt can be used in conjunction with the partial conditioning step. By selective bactericide is meant the property of the reagent to destroy putrefaction-causmg organisms without impairing the activity of the living yeast-type organisms used for partially conditioning the stock. Among the various silicofiuoride salts which can be used simultaneously with the microorganism treatment of the glue stock without destroying the yeast and/or yeast-like organisms are the sodium, potassium and ammonium compounds. The alkali metal salts are preferred and sodium silicofluoride is particularly desirable. From0.5 to 3% by weight is generally sufficient to prevent spoilage of the stock and permit the conditioning to proceed as desired. Excellent results are achieved with the use of about 1% by weight of sodium silicofluoride on the basis of the weight of glue stock. In terms of overall concentration, when three weights of water are used, this to achieve a more effective distribution. The inoculum of microorganisms on the basis of the weight of glue stock can be varied as between 0.5 to 3% by Weight.

Amounts in excess of 3% can be used but no significant advantage is obtained thereby other than a slight acceleration of the partial conditioning step which does not Warrant the use of additional amounts. It has been found that about .8 to 1.5% by weight give very good results and about 1% by weight is preferred. This latter amount calculated on the basis of overall concentration using three weights of water to cover the stock amounts to about 0.25%

The time required for completing the partial conditioning of the glue stock is somewhat dependent upon tem perature as well as other factors as the type and amount of inoculum being used. For practical considerations it may be desirable to use room temperature (about 70 F.).

The temperature can be raised or lowered however within limits readily determinable by those skilled in the art as conducive to maintaining the organisms in living form in the presence of the selective bactericide. By way of illustration, it has been found that the partial conditioning of cattle hide stock could be accelerated by 1 to 2 days by maintaining a vat temperature of F. as opposed to room temperature when using 1% of bakers yeast and sodium silicofiuoride respectively. It is thus seen that the temperature for the partial conditioning step is not critical but can be varied in accordance with desired practices.

The partial conditoning step can be further enhanced, if desired, by the addition of well known nutrient materials such as glucose, sucrose, lactose, etc., which favor the more rapid growth and thereby promote the action of the microorganisms on the glue stock.

The"partial conditioning or pretreatment of the glue stock with microorganisms referred to herein is usually completed in from 2 to 4 days. This stage of the processing can be readily recognized by a simple physical examination of the glue stock in that the stock contains a loosened epidermal layer from which the hair can be readily slipped by the application of slight pressure by the fingers.

Upon completion of the partial conditioning of the glue stock, the aqueous .phase containing the microorganisms, bactericide, and other substances removed from the glue stock is drained from the vat and the stock, after washing, is again covered with water. Lime is added thereto and the material is kept in the vat preferably at room tempera ture until the conditioning of the stock is completed for glue extraction.

The amount of lime should be in excess of the quantity required for saturation of the Water at all times during the liming period. From 3 to 10% by weight based on the initial glue stock weight can be used and larger amounts are not particularly harmful. It is preferred, however, to use about 4 to 6% and excellent results are achieved by the addition of about 5%. The amount of water added is again between 2 and 4 times the stock weight and preferably about 3.

Depending upon the type and condition of the stock being processed, the conditioning becomes complete in from'2 to 12 days and glue can be satisfactorily etxracted therefrom. As seen from the data in the examples, however, the viscosity of the glue from lime treatment extending from 2 to 7 days shows a progressive increase in value indicating that a liming period of about 5 to 7 days is preferable over the shorter periods for the production of a balanced glue. This is in sharp contrast to the conventional liming period heretofore requiring from 60 to days for conditioning the stock satisfactorily.

The expression complete conditioning or conditiom ing as used herein is to be distinguished in meaning from partialconditioning used in describing the eifect'produced by the action of microorganisms previously defined.

readily cut by the thumbnail. At this point the collagen of the stock is highly susceptible to the action of hot water and is readily extracted from the tissue and converted to;

glue.

While I donot desire to be limited to any explanation regarding the theory or reaction mechanism involved in the lime conditioning of glue stock, it is believed that the lime causes the disintegration andseparation of non-glue forming proteins which in turn leave the hide more porous so that hot water can permeate the stock more readily and convert the collagen to glue. This explanation is feasible since it is known that albumins and globulins are soluble in alkaline solutions and thus would be extracted and removed from the stock under conditions of liming. Mucins also tend to become soluble'in alkali and hence would be removed at the same time. Regardless of the mechanism involved, the glue maker is required to allow the stock to remain in lime solutions from 60 to 1 20 days in order to satisfactorily condition the stock for glue extraction. It is further believed that the action of living microorganismsherein utilizedas .a preliminary step serves to open up the protein structure of glue stock thereby permitting a more rapid penetration of lime or other chemical reagents. As previously stated, however, the protein structure modification which is brought about is definitely not attributable to proteolytic activity.

The completely conditioned stock is drained to remove the lime solution and is Washed and rinsed inrunning water for about oneor two hours. The organism-lime conditioned stock can be extracted, after neutralization of the lime with hot water in accordance with conventional practice. The neutralization is commonly carried out by the use of hydrochloric acid orsulphurous acid; the latter being preferred since an added advantage ofbleaching the glue as well as a preservative action is obtained. Itis preferred, however, to extract the stock conditioned in accordance with the present invention by using ammonium carbonate for adjusting the pH of the extraction mixture. In lieu of ammonium carbonate, the same results may be achieved by using ammonia and carbon dioxide.

The use of ammonium carbonate for removing the last traces of lime and for essentially neutralizing the remaining alkalinity of the organism-lime conditioned stock has been found to possess several important advantages. in the first place, there is no need for careful pH control or measurements since the pH falls naturally to a level (9.-9.5) which is conducive for satisfactory extraction of the glue upon evaporation of the volatile ammonium hydroxide which is formed. Excessive deplumping of the stock tissue is also avoided which results in enhancing extractability of the glue. Further, calcium carbonate which is precipitated can be readily removed without extensive mechanical wash mill operations. Another obvious advantage is the fact that a glue of lower ash content is obtained by virtue of the simplified removal of inorganic salts. A further improvement in glue qualityis achieved by eliminating the use of sulfur compounds such as sulfur dioxide or sulfurous acid which normally makes it difficult to maintain the low sulfur requirement demanded by many glue users.

The amount of ammonium carbonate required is not critical as long as a suflicient quantity is used to precipitate the residual lime as calcium carbonate as previously stated. About 1 to 5% by weight calculated on the basis of the original weight of the glue stock is generally sufiicient but the use of larger amounts is not detrimental in view of the levelling on of the pH at between 9 and 9.5 regardless of the amount added. As previously stated, the pH gradually approaches neutrality as the volatile component, ammonium hydroxide is evaporated.

It is preferred to allow the stock thus treated and covered with water to stand for about 12 to 24 hours after which it is drained to. remove the neutralizing solugreases 6 tion and precipitated salt. The stock is preferably rinsed at this point to remove adhering calcium carbonat'eand the glue liquor is then extracted by conventional hot Water cooks at progressively increasing temperatures from 160 F. up to theboiling point of Water. The extracted glue liquor can be further processed to yield the dried product, if desired, by following the Well known procedures of chilling, drying, grinding, etc.

This invention is further illustrated by the following specific examples.

Example I A pound batch of salted hide pieces was washed to remove the salt, debris, etc., and the washedstock was covered with three times its weight by water. An aqueous slurry containing 0.3 pound of bakers yeast (National) was added. The same quantity of sodium silicofluoride was added to the vat and the mixture was held at 95 F. for 3 days. At the end of this period the hair could be readily slipped from the pieces so the stoclcwas drained and washed and again covered with approximately the same quantity of water.

A 5% by weight liming mixture was formed by adding 1.25 pounds of lime and stock was soaked for .2 days at room temperature. The liquid was drained off and rinsed in running water for an hour. "again covered with water containing one pound of ammonium carbonate and the mixture was allowed to stand overnight (18 hours). The neutralizing solution was then drained and the stock rinsed once more in running water to remove adhering calcium carbonate. The glue was readily extractable by conventional methods and the data is summarized as follows:

Fraction Temp. Yield Jelly Vlscosity pH of Number F1). (Hrs) (lbsx) (gmsJ (mp3 Glue 1- 160-175 6 47 370 94 7. 2 6 1. 67 460 92 7.3 G 1. 440 7.4 6 i l. 56 165 63 8. 0

The yield of glue was 21% on an as received basis.

The average gel strength was 353 grams and the average viscosity, 82 millipoises.

In a .series of replicate runs following the specific procedure set out above excepting that the holding period in lime was extended from 2 days to 3, 5 and 7 days respectively, the following data was obtained:

5 THREE DAY LIMING PERIOD The stock was Cooking i Fraction Temp. Yield Jelly Viscosity pH of Number F.) i (lbs) (gms.) (mu) Glue 6 1.07 583 112 7.2 s; 1 48 510 127 7.3 s 1 55 370 a 125 7.5 6 1 25 180 7.7

DAY LIMING- PERIOD SEVEN DAY LIMING rumor) 1 -175 6 1. 31 432 168 7.3 10 2 170-190 6 1. as 449 168 7:6 3 -205 a 1.41 326 198 7.5 4, 212 s .so, 304 17s 7.7

Average 392 17s a 75 It is seen from the above data. that the viscosity increases directly as the liming period is extended and that the preferred quality or balanced glues are obtained when a liming period'of to 7 days is used. Overall yields in all runs were in excess of Example II Fifteen pounds of fresh cattle hide trimmings were washed and put into 50 pounds of water containing .15 pound of bakers yeast (Saccharomyces cerevisiae) and .15 pound of sodium silicofluoride. The stock was held at room temperature for 5 days and then drained, washed and covered with water. One-halt pound of lime was added and after a holding period of 7 days at room temperature, the stock was treated following the procedure set forth in Example I using 5% by weight of ammonium carbonate. A glue yield of 21.4% was obtained having an average gel strength of 426, viscosity 161 and pH 7.4.

Example III Twenty-five pounds of salted hide trimmings were treated as in Example I up to the liming step. In this run the holding period in 5% by weight of lime was extended to 10 days and the sulfurous acid method of neutralizing the conditioned stock was used. The procedure included the draining and rinsing steps to eliminate the residual lime after which the stock was covered with water and sulfur dioxide was bubbled in until the pH reached 8.3. The water was thereafter drained and the tissue rinsed to remove adhering calcium sulfite. The glue stock thus prepared was readily extractable so shorter cooking periods and lower temperatures were used as indicated by the data in the following table which summarizes the extraction procedure and results.

A pound batch of salted cattle hide stock was Washed and covered with 3 weights of water containing .25 pound of hydrogen peroxide. After standing for about 3 hours at 95 F., 0.25 pound of bakers yeast (National) together with a like'amount of glucose was added and the lot was held at 95 F. for 24 hours. Sodium silicofluoride (.25 pound) was then added and after 3 days at the same temperature (95 F.) the hair could be easily slipped. The stock was drained, rinsed and again covered with water, after which 1.25 pounds of lime was added. After standing in the vat for 7 days at room temperature F.) the stock could be readily cut by the thumb nail so the material was drained, rinsed and covered with fresh water to which 2 pounds of ammonium carbonate was added. After standing for a period of 24 hours, the stock was cooked to remove glue in the usual manner. A total of 5.4 pounds of glue was recovered from the four 6-hour cooks, the average gel strength of which was 451 and average viscosity 152.

Example V A 25 pound batch of fresh hide stock was treated as described in Example IV excepting that .25 pound of hair ball material was used in place of the bakers yeast. This material is known to be an excellent source of Mycoderrna and Torulopsis organisms. After contact with the microorganisms for 4 days at 95 F. the stock was limed as 7 the glue. The yield of glue was 5.2 pounds, strength 441,. and average viscosity 144.

While in the foregoing specification this invention has been described in considerable detailv and a number of specific embodiments have been set forth, it will be apparent to those skilled in the art that many of the specific details and embodiments can be varied widely without departing from the broad idea of the invention. I I

I'claim: I t

1. In a process for conditioning collagen-bearing animal tissues for glue extraction, the steps of exposing the tissues to the action of added living yeast-type organisms to partially condition the same and thereafter liming said tissues to complete the conditioning.

2. The process of claim 1 wherein the. organisms are 0 the genus Saccharomyces. I

3. The process of claim 1 wherein the organisms are of the Mycoderma and Torulopsis species.

4. In a process for conditioning glue stock to prepare the same for glue extraction with hot water, the steps of exposing the stock to the action of an aqueous bath containing living yeast-type organisms and a selective bac' tericide to partially condition the same, and thereafter treating the partially-conditioned stock with lime to complete the conditioning for glue extraction.

5. .The process of claim 4 in which said glue's tock is cattle hide stock.

6. The process of claim 4 wherein the yeast-compatible bactericide. is an alkali metal silicotluoride salt.

7. The process of claim 4 with the added step of sterilizing the glue stock with hydrogen peroxide prior to the partial conditioning step. I 8. In a process for conditicr'ng glue stock for preparing the same for glue extraction with hot water, the steps of treating said stockwith an aqueous mixture conaverage gel .taining from 0.5 to 3% of the initial stock weight of yeasttype microorganisms and from 0.5 to 3% of sodium silicofiuoride to partially condition said stock, contacting the partially-conditioned stock with an aqueous liming mixture containing lime in an amount of from 3 to 10% of the stock weight for a suificient period to fully condition said stock for glue extraction, and recovering the glue therefrom.

9. The process of claim 8 wherein the partial-conditioning step is carried out at about F. for from 2 to 4 days.

10. The process of claim 1 in which the yeast-type microorganisms are predominantly Saccharomyces cere visiae.

11. The method of obtaining glue from hide stock which comprises partially conditioning said stock for from 2 to 4 days in the presence of added living yeast-type microorganisms and an alkali metal silicofiuoride salt liming the partially conditioned stock for about 5 to 10 days to complete the conditioning and recovering the glue therefrom.

12. The method of claim 11 wherein the glue recovering step includes adding sufiicient ammonium carbonate to the conditioned stock to lower its pH to between 9.5 and 9.0 and thereafter cooking the stock in hot water.

13. The method of obtaining glue from cattle hide stock which comprises sterilizing the stock with hydrogen peroxide, subjecting the sterilized stock to the action of an aqueous mixture containing about 1% by weight of bakers yeast and about the same amount of sodium silicofiuoride for from 2 to 4 days at about 95 F. to partially condition the stock, removing said aqueous mixture, covering said stock with water containing about 5% of the stocks weight of lime and holding said stock therein for about 5 to 10 days to complete the conditioning for glue extraction.

1.4. The method of claim 13 with the added steps of washing the limed stock, adjusting the pH to between 9.5 and 9.0 with ammonium carbonate and thereafter extracting the stock with hot water.

No references cited. 

1. IN A PROCESS FOR CONDITIONING COLLAGEN-BEARING ANIMAL TISSUES FOR GLUE EXTRACTION, THE STEPS OF EXPOSING THE TISSUES TO THE ACTION OF ADDED LIVING YEAST-TYPE ORGANISMS TO PARTIALLY CONDITION THE SAME AND THEREAFTER LIMING SAID TISSUES TO COMPLETE THE CONDITIONING. 